Glass polishing equipment



April 28, 1959 A. J. PAcloNE GLASS POL-ISHING EQUIPMENT FiledJan. 2o, 195s www IN VENTOR.

United States Patent O GLASS POLISHING EQUIPMENT Albert J. Pacione, La Salle, Ill.

Application January 20, 1958, Serial No. 710,045

3 Claims. (Cl. 51-197) The present invention relates to glass polishing equipment. This specification is a continuation-in-part of my co-pending application, Serial Number 539,061, led October 7, 1955, now abandoned.

The invention is particularly directed to improvements in felt polishing pads of a type now commonly employed in the manufacture of at plate glass, and it is the primary aim of the invention to provide improved means whereby plate glass sheets may be polished more economically than heretofore by a reduction of the' amount of felt wasted fin the operation of the polishing equipment.

It is well known, of course, that the plate glass manufacturing industry is an extremely active one, particularly in the United States. The polishing equipment commonly employed for the purpose is of a well known type which has long since become more or less standardized and conventional. In such equipment the flat surfaces of the glass are polished by a mechanism employing a plurality of rotary, disc-like metallic polishing blocks. In a conventional machine, these are about 221/2 in diameter and approximately 21/2 thick. The at face surfaces of these discs are covered with a sheet of polishing felt, ordinarily between an inch and an inch and a half in thickness. It is conventional practice to cut the felt pads to a diameter somewhat greater than the diameter of the block, and to secure the felt disc to the block by drawing the marginal edge of the felt pad around the outer circumference of the polishing block in a press. The marginal edge of the felt is then clamped to the block by a metallic ring extending around the entire assembly.

With prior art apparatus of the type generally indicated above, it has long since been observed that the felt pads quickly harden and develop cracks in a circular zone corresponding to, or slightly smaller than, the outer edge of the polishing block. When such cracking occurs, the felt must be replaced to avoid danger of breaking the glass being polished. It follows that the felt must be discarded long before it is worn out, and a serious economic loss results. The seriousness of this loss will be apparent when it is pointed out that thousands of dollars worth of felt are used each month in a typical large commercial glass plant, yet it is quite customary for such a plant to be required to replace the felts, on an average, even before they have been worn to half their original thickness.

It is accordingly a principal object of the invention to provide an improved polishing pad for conventional glass polishing equipment, so designed and constructed as to reduce the amount of felt used, and to simultaneously reduce the likelihood of breakage of glass due to cracking of the polishing felts. A further object of the invention is to achieve the above results by the provisions of an improved pad so designed and constructed that it may be used in connection with polishing machines of the conventional design now commonly employed in the industry.

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The present invention departs from the conventional practices outlined above by the provision of a felt polishing pad provided with at least one circumferential notch extending around the pad adjacent the periphery of the polishing block, in the vicinity of the relatively hard bend formed by drawing the felt pad around the edge of the metal block. It has been found that such notching of the marginal edges of the felt largely overcomes the premature deterioration of the pads which otherwise occurs, yet does so without sacrifice of the wear resistant qualities of the relatively hard bend portion at the edge of the pad.

Three variations of the present invention are illustrated in the drawings of this specification, wherein:

Figure 1 is a fragmental cross sectional View of one example of a felt polishing pad constructed in accordance with the present invention. The view is taken through the edge of the pad and the block, showing the pad provided with one circumferential notch located just outside the edge of the block, and a second notch between the bend portion of the pad and itsv marginal mounting skirt;

Figure 2 is a similar fragmental cross sectional view of a modifiedv polishing pad employing two circumferential notches in alternative positions;

Figure 3 is a similar fragmental View of another modied pad employing three circumferential notches, and

Figure 4 is a similar view showing the approximate cross sectional contour of the pad of Figure l after an interval of use.

In Figure 1 the polishing pad is preferably a at circular felt sheet 10 of uniform thickness, and of diameter about live inches greater than the diameter of the block. The felt is secured on the face surface 11 of a metal polishing block 12 by positioning the pad concentrically on the block and then pressing a retaining ring 13 over the pad to form a bend 14, in which the grain of the felt curves around the corner edge of the block to terminate in a marginal skirt 15 around the upright walls 16 of the polishing block. One or more circumferential slits 17, 18 are then cut in the periphery of the pad. Preferably, these slits should be of depth at least half the thickness of the felt, it being understood that the tension on the fibres of the felt will be such as to cause the slits to open up into notches of substantially the size and shape shown in Figure 1. For best results, these notches should be located outside of the central polishing area of the face 19 of the pad, in a zone close to the bend 14.

In use, a pad formed as in Figure l tends to wear to the shape of Figure 4, with the notch 17a opening wider and wider, and the notch 18a tending to grow narrower as the surface 19 wears down to 19a, 19b, 19e to 19d, consecutively. Thus, the relatively hard bend portion 14a of the felt moves gradually inwardly but serves as a buler outside the notch 18 until the felt is worn almost through.

In the form of the invention shown in Figure 2, the polishing pad 20 is mounted on the face surface Z1 of a metal polishing block 22 by a retaining ring 23 as heretofore described. The bend 24, in which the grain of the felt curves around the edge of the block, is notched at 25, with a second notch 26 cut in the skirt 27 just beloW the ring 23 by which it is secured to the upright wall 28 of the polishing block. One or more of these circumferential slits may be cut in the periphery of the pad as desired. In the form of the invention shown in Figure 3, notches 29, 30 and 31, are provided.

While the notches contemplated by this invention may be formed by cutting segments from the felt, if desired, it will be understood that it is ordinarily only necessary to slit the felt with a knife at the desired points, since the tension of the fibres of the felt will cause the slits to draw open, as heretofore described.

It is to be observed that with this invention, the curvature of the grain of the felt causes a relatively hard bend to be retained as a buffer around the edge of the polishing face of the pad. This hard bend or buer area has beenfound to contribute to the wear-resistant qualities of the pad, while the circumferential notches have been found to overcome the tendency of felt to crack and' disintegrate. In practice, this means that polishing'pads of any given thickness are not subject to the premature deterioration heretoforeregarded as inevitable. TheA result is that the pads may be used until they are worn to a substantially greater extent than practicable in the past'.

Obviously, this eects substantial savings in the cost of: felt employed in any polishing establishment. Also, since it permits longer'runs onffelt pads of the same-thickness, it effects secondary savings in reducing the down time of the machines; that is, the-intervals in which equipment is out of service for removal and replacement of the felts.

Having thus described my invention, what I claim as new and desire to protect by United States Letters Patent 1. In a glass polishing machine including a polishing block having a relatively at circular face bounded by an upright cylindrical side wall, the combination of a polishing pad of resilient brous felt, said pad having a at polishing zone overlying thel flat circular face of the polishing block, and a relatively hard edge bend interconnecting said polishing zone with an edge skirt clamped to the side wall of this polishing block; saidpadbeing of generally uniform thickness throughout but with at least one circumferential notch adjacent the edge bend of the pad and in a position spaced outwardly from central area of the polishing block; the depth of one notch being at least half the thickness of the felt in the polishing zone.

2. As an article of manufacture, a glass polishing pad consisting of a single, one piece, integral sheet of resilient fibrous feltV having a generally circular central polishing zone of substantially uniform thickness; atleast one notch in the surface of the felt in the circumferential area extending around saidl polishingv zone, and an outer edge skirt adapted to be folded over the outer circumferential edge of a polishing block.

3. As an article of manufacture, a glass polishing pad consisting of a single, one piece, integral sheet of resilient fibrous felt of substantially uniform thickness throughout with a generally' circular control polishing zone surrounded by at least one circumferential notch of depth at least half the thickness of the felt.

References Cited inthe file of this patent UNITED STATES PATENTS 891,198 Wadsworth June 16, 1908 1,798,633 Rotheram Mar. 31, 1931 1,946,355 Miller Feb. 6, 1934 

